Tanning



'tions.

UNITED STATES PATENT OFFICE.

CONRAD VARLEY GREENWOOD, OF BLUNDELLSANDS, NEAR LIVERPOOL, ENGLAND.

TANNING.

No Drawing. Application filed July 28,

T 0 all whom it may concern:

Be it known that I, CONRAD VARLEY Gnnnxwooo, a subject of the King of Great Britain, residing at Blundellsands, near Liverpool, in the county of Lancaster, in the Kingdom of England, have invented certain new and useful Improvements in Tanning, of which the following is a specification.

It is well known that in the tanning of skins for the production of leather by interaction of the skin substance with tannin in various forms, it is imperative to graduate these actions with various devices, generally by a succession of steps of increasin concentration of the extract or tannin. llence the ordinary process is one of long duration requiring in the case of sole leather, 6. g., a period of several weeks or even months for the due carrying out of the successive treatment.

It is the object of the present invention to provide improved tanning methods embodying a more rapid process and producing a superlative quality of leather.

United States Patent No. 1105195 describes a process of producing a new or improved mucilaginous material. This specification suggested a possible application of tne product in connection with tanning but it gave no details of such application, nor did it disclose the fact that the product exerted any action different to the action of tannin in the direction of speed of tanning or otherwise.

I have succeeded in devising processes employing hemicellulose e. g., that obtained from the locust bean and similar colloids in such manner as to attain quite novel results. It is well known that tannin in its various forms interacts with certain soluble colloidal carbohydrates to form compounds which are obtained as flocculent precipitates, or a more massive coagulum which retains much water in combination.

With certain carbohydrates of the hemicellulose class, the precipitant or coagulum has been observed to have the distinct characteristic of separating at lower temperatures in homogeneous opaque masses which are again liquefied on raising the temperature to form transparent highly viscous solu- Such compounds or their manufacture are dealt with in the above-mentioned patent specification No. 1105195.

- According to the processes which I have devised, it is possible to conduct tanning in such manner as to attain very considerable Specification of Letters Patent.

'hence the process Patented Aug. 10, 1920.

1915., Serial No. 42,339.

advantages depending on the fact that the combination of tannin with such carbohydrates is of a weaker order than the combination of tannic acid with gelatin and nitrogenous colloids of the gelatin group. Hence when gelatin or a prepared animal skin is placed in contact with these compounds, both being in the normal stage of hydration and in presence of water, the superior attraction of the nitrogenous colloid exerts itself, and it combines with the tannin, the carbohydrates being displaced.

For obvious reasons, this process of combination by displacement is gradual, and

of restrained tannage enables me to carry out the industrial process with very much increased rapidity.

The processes vary according to cumstances and the following are methods of treatment (1) The skins 0r hides having been limed, unhaired, and flashed, are rounded and washed in a weak lime liquor in the ordinary way and are then ready for deliming.

This deliming is best carried out by suspending in a. rectangular pit. A suitable deliming bath is made as follows for butts, 1200 to 1500 gallons of water 10 lbs. acetic, formic or hydrochloric or other suitable acid. The goods should be suspended for 24 hours.

It is extremely important that the deliming or acidifying .hould receive careful attention, and should be carried somewhat further than when tanning is by ordinary and older methods.

The goods after deliming, should be rinsed in water to remove the soluble lime salts and are then ready to tan.

For the preparation of the tanning material, the processes may vary according to the circumstances and the following are typical examples :--The hemicellulose is precipitated by means of the tanning extract or tannin and in some instances the mixture of the two materials is taken and used full strength. In others the coagulum or precipitate is allowed to separate. This is then dissolved in warm water and used as follows The goods are laid fiat on a wooden board and are painted over on both sides with the aforesaid compound. making the application with a suitable fiat brush. They are then laid perfectly fiat in the bottom of a clean pit. An application of the aforesaid compound at least inches thick should be made between each pair of butts and same the cirtypical lulose class which,

laid on top of each other, flesh to flesh, the pit afterward being filled'with the said solution to about 1 ft. above the uppermost pair of utts.

The goods should be left for 24 hours in this way and then carefully taken out on a sloping table leading into the pit so as to avoid any loss, the stirred and the goods put back again, one at a time. The goods are left in the mixture, strengthening if necessary by a further quantity of extract until a further penetration has been effected, this usually requiring at to days when the goods on cutting will be found to be tanned completely through.

The goods are now removed, the surplus material slicked off and are then washed in water at, a temperature of about centiin a100 barkometer liquor with valones and myrobalans, or other suitable material.

(2) The coagulum of hemicellulose tannic acid compound or mixture as already described may alternatively be used either full strength or dlssolved in water and added to the prepared hides or skins 1n a revolvlng drum. By this method the period of tanning is considerably reduced and the hides are space of about 24 hours.

(3) The more flocculent precipitant may be prepared, separated and collected, and then diffused in Water in a suitable pit or bath, into which the prepared skins are placed and left at rest with occasional hanling or strengthening if found necessary until the reaction is complete.

(4%) The hemicellulose material may also be acted manner. Alternatively, any suitable coll-oidal body may be used in place of the hemicellulose material for the purpose of interaction with natural or synthetic tanning agents provided that the result is such as to exhibit the restraining action above described.

I use the words restraining colloid to denote a colloid preferably of the hemicelexhibiting the property of being able to combine with tanning.

In other words, in its broadest form the invention covers processes of tanning by organic materials in which the process .s considerably accelerated by thus designidly employing a colloidal restraining agent 11 conjunction with such tanning. The best olloidal materials appear to be the soluble iemicelluloses above describedbut the inmixture thoroughly well 1 vention also extends to other colloidal ma terials exhibiting similar properties.

I declare that what I claim is restraining colloid but time.

2. A process of tanning in which a restraining colloid is employed in conjunction with a tanning solution which is stronger than would be possible if the restraining tanning tanning time.

3. A process of tanning in which a hemi cellulose obtained from the locust bean is employed in conjunction with a stronger tanning solution than usual so that at least as good a tanning effect is obtained but the time is considerably shortened.

4. A leather in a mucilagpaste consisting of a compound of hemicellulose and tannin and said butts are immersed in a liquor, containingthe same ingredients in solution.

5. A process of tanning in which the goods are treated with a compound composed of vegetable restraining colloid and a tannin, and immersing the ed in a liquor containingthe same ingredients in solution.

6. The herein described process of tanning which'consists in employing an abnormally strong tanning solution in conjunction with a restraining colloid of vegetable origin under such conditions that the same tanning effect is obtained as in the usual but in a very much shorter he herein described process of tanning which mally strong tanning solution in conjunction with a of combining 7 tion and thereafter gradually. imparting the same to the leatheror hide being treated.

I goods are first treated with a vegetable restraining colloid and subsequently treated with a tanning agent of, such strength as would injure the goods except for the presence of the restraining colloid.

In witness whereof, I have hereunto signed myname this 15th day of J uly 1915, in the presence of two subscribing witnesses.

00mm VARLEY GREENWOOD. WVitnesses: V Y 7 i H. Srronrnmen,

. BnnsroN.

goods thus treat- 

